Control system



W. G. COOK CONTROL SYSTEM July 19, 1949.

, Filed June 14, 1944 2 Sheets-Sheet l ww um &

uuuuuu II uuuuuuu'l INVENTOR Wfl/ara. 600K.

ATTORN WITNESSES:

July 19, 1949. w. a. cow 2,476,839

CONTROL SYSTEM Filed June 14, 1944 2 Sheets-Sheet 2 07 we we WITNESSES:INVENTOR a? %7 MY/qrc/ & COOK.

n V I I Y a w 1 I, A ORNEY Patented July 19, 1949 UNITED STATES PATENTOFFICE CONTROL SYSTEM Application June 14, 1944, Serial No. 540,237

14 Claims.

M invention relates, generally, to control systems, and it hasreference, in particular, to automatic screwdown control systems such asused for controlling the relative movements of rolls in steel rollingmills.

Generally stated, it is an object of my invention to provide anautomatic screwdown control system which is simple and inexpensive tomanufacture and is easy to install and operate.

More specifically, it is an object of my invention to provide anautomatic screwdown control system which affords automatic accelerationand deceleration of the screwdown motor with a minimum of plugs in thelimit switch plug board.

An important object of my invention is to provide for reducing thenumber of control circuits necessary to effect automatic control of thescrewdown motor of a rolling mill.

Another object of my invention is to provide for reducing the number ofcontact members required in a limit switch for controlling a screwdownmotor without reducing the effectiveness of the limit switch.

Yet another object of my invention is to provide for incorporating ashort-cirouiting device in each of the receptacles of the limit switchplug board so as to eliminate the requirement for dummy plugs betweenpass plugs in order to complete an operating circuit.

Still another object of my invention is to provide an improved screwdowncontrol system wherein a single limit switch may be used in conjunctionwith a plurality of plug boards for setting up a plurality of differentroling schedules independently of each other, and while rolling orotherwise.

Another important object of my invention is to provide for incorporatinga reliable short-circuiting switch in each of the plug receptacles ofthe limit switch so as to preclude the necessity of using dummy plugsbetween the pass plugs.

A further object of my invention is to provide a compact and reliablepush button switch for each plug receptacle which has a definite wipingaction so as to prevent the occurrence of an accidental open circuit.

A still further object of my invention is to provide a plug andreceptacle arrangement wherein contacts of the receptacle are normallyshort circuited and the short-circuitin means is actuated by theinsertion of a plug in the receptacle to remove the short circuit onlyafter the contact members of the receptacle are engaged by contactmembers of the plug.

Still another important object of my invention is to provide forstopping a screwdown motor when it is operating in the direction tobring the rolls together and provide a remotely operable vernieradjustment for attaining the desired final position of the rolls.

Yet another important object of my invention is to provide for using adifferential drive for operatively connecting the limit switch of ascrewdown control system to the screwdown motor and provide foradjusting the differential drive to obtain Vernier adjustments betweenthe relative positions of the screwdown motor and the limit switch.

It is also an important object of my invention to provide for operatingan adjustable limit switch in response to movement of an object whoseposition is to be controlled thereby, by means of a synchrotie systemand a differential mechanism having a driven element operated from thesynchrotie system, a driving element operating the limit switch and arotatable control element which may be remotely actuated to cumulativelyor differentially vary the position of the object from the positionindicated by the limit switch.

Other objects will in part be obvious, and will in part be explainedhereinafter.

In accordance with one embodiment of my invention, the operation of ascrewdown motor actuating one of a pair of relatively movable rolls iscontrolled by directional relays and speed control means. A limit switchis provided havin a movable contact arm for engaging a plurality ofspaced contact segments which are arranged in spaced apart tracks fordetermining energizing circuits for the directional relays and speedcontrol means, respectively. A plurality of pass control relaysselectively controlled by a pass selector switch are connected to thesegments of the limit switch by means of plugs and receptacles forcontrolling the operation of the screwdown motor. The receptacles areprovided with shortcircuiting devices which normally provide anenergizing circuit for one or another of the directional relaysdepending on the position of the contact arm and which of the passcontrol relays has been operated. The contact arm of the limit switch isoperatively connected to the screwdown motor by means of a synchrotiesystem and a differential drive which has a control element remotelyoperable to vary the position of the screwdown motor from that indicatedby the position of the contact arm. By reason of the short-circuitingmeans in the receptacles a plurality of groups of receptacles may beconnected to the contact segments of the limit switch independently ofeach other so that a plurality of different rolling schedules may be setup independently of each other without effecting an actual rollingoperation.

For a more complete understanding of the nature and scope of myinvention reference may be made to the accompanying drawings in which:

Figure l is a diagrammatic view of an automatic screwdown control systemembodying the invention in one of its forms;

Fig. 2 is a front elevational view of a receptacle in one of the plugboards embodying the features of the invention;

Fig. 3 is a sectional View taken along line 111-111 of Fig. 2;

Fig. 4 is a front elevational view of a plug which is disposed to bepositioned in the receptacle shown in Figs. 2 and 3;

Fig. is a sectional View of the plug taken along the line V-V of Fig. 4;and

Fig. 6 is an enlarged sectional view of the shortcircuiting device shownin Fig. 3 in a partially operated position so as to illustrate theoperating action of the switch member.

My invention comprises an improvement of and a simplification of thescrewdown control system described and claimed in Patent Nm 1,764,312which issued on June 17, 1930, to Harold C. Jenks and is assigned to theassignor of the present invention.

Referring to Fig. l, the reference numeral II] may denote generally aroll stand such as used in steel rolling mills wherein relativelymovable rolls I I and I2 are rotatably supported in a frame structureI3. Relative movement of the rolls to change the distance between themmay be obtained in any suitable manner, such as by means of a screwdownmotor I5 which may be operatively connected to the journals of the rollI2 through'screw mechanisms I6 so as to provide for raising and loweringthe roll I2 relative to the roll II. The driving means for the rolls isnot shown but may be connected, for example, to the roll II through theshaft I8.

Operation of the screwdown motor I5 may be effected by connecting thearmature thereof to the armature of a generator 2| which may be drivenby any suitable prime mover (not shown) and provided with a fieldwinding 22. The field "winding 23 of the screwdown motor may beconnected to any suitable source indicated by the plus and minusterminal connections.

The direction of operation of the motor I5 may be controlled by means ofraise and lower directional relays 25 and 26 which may be operable tochange the connections of the generator field winding 22 and a source ofexcitation indicated by plus and minus terminals so as to provide foroperation of the motor to raise and lower the movable roll I2,respectively. Means such as the interlock relay 2! may be provided forpreventing operation of the raise relay 25 in the event that thescrewdown motor I5 overshoots when operating in the downward direction.

form of a regulator 28 having an operating winding 29 for actuating aplurality of contact members 28a, 28b, 28c, etc., to progressivelyinsert steps of a control resistor 30 in the field circuit of thegenerator 2| in a well known manner. A pilot generator 3| may beutilized in connection with the speed control relay 28, being connectedto the screwdown motor so as to provide a retarding force proportionalto the' speed of the screwdown motor.

In order to control the operation of the directional relays 25 and 26and the speed control relay 28 in accordance with the direction anddistance of the movable roll l2 from the desired operating position, thelimit switch denoted generally by the numeral 32, may be provided.

The limit switch 32 may comprise a pair of tracks 33 and 34 positionedin spaced relation upon a suitable insulating support and disposedatively connected to the screwdown motor I5. The tracks may comprise aplurality of contact segments 33a, 33b through 33p, 33g and 331, andsegments 34a, 34b through 34p, 34g and 341', respectively.

Only a few of the contact segments, which may actually number on theorder of I38 in each track, are shown, in order to simplify thedrawings, but it will be understood that the segments actually shown areintended for the purpose of illustration only and the invention is notlimited to any particular number thereof. The segments in the tracks 33and 34 are preferably provided with overlapping end portions by havingthe adjacent ends thereof inclined in parallel relation so as to providea substantially continuous supporting and contact surface for themovable contact arm 35 which is disposed to move along the tracks inbridging relation therebetween.

Resistance means 36 comprising a plurality of control resistors 36a,361) through 3620 and 3Bq may be connected in bridging relation betweenadjacent segments of the track 34 in order to provide a variableimpedance control circuit for the regulator 28 in a manner whichhereinafter will be described in detail. By connecting the resistancemeans 36 intermediate the ends of the segments of track 34, andpositioning the segments thereof in staggered relation to the segmentsof track 33, it is possible to reduce the number of connections hithertorequired, and still maintain uniform relations between the resistancemeans and the control segments 33 regardless of the direction ofmovement of the arm 35. Electrical connection may be made to the contactarm 35 in any suitable manner, such as by means of the operating shaft31 and a collector 38.

In order to provide operating circuits for the directional relays 25 and26 from the contact arm 35 through predetermined portions of the limitswitch track 33 depending on the position of the movable roll I2 fromthe desired operating position, and hence provide for adjusting the rollI2 to a predetermined number of predetermined pass positions in a #1schedule, a plurality of pass control relays 40, 4| and 42 may beprovided in one group, having operating windings 43, 44 and 45,respectively. These pass control relays may be controlled by means of apass selector switch 41 having a movable contact arm 48 for engaginganyone of a plurality of stationary contact members 47a, band 470, toselectively provide predetermined circuits through the tracks 33 and 34for determining the operation of the motor I5. An additional contactmember 41d may be provided for controlling the operation of a specialpass control relay 50 which may be used to determine the minimum spacingbetween the rolls II and I2.

In order to provide for setting up a plurality of different rollingschedules, additional groups of pass control relays may be provided suchas may be represented by the group of additional pass control relays 52,53 and 54, and which may be used for setting up a diiferent rollingschedule designated as schedule #2 as distinct from schedule #1 which isprovided by the pass control relays 43 through 45. Selection of adesired group of pass control relays to be effective may be made bymeans of a schedule selector switch 58 which provides for selectivelyconnecting the operating windings of either the schedule #1 or schedwe#2 pass control relays to the positive terminal of the source.

The energizing circuits for the directional relays 25 and 2B and thespeed control relays 28 may be determined by means of a group of passplugs represented by the plugs 60, 6| and 62 which are disposed to bepositioned in different ones of a group of receptacles represented bythe receptacles 64, 65, 66, 61 or 68. In this instance each of thereceptacles is provided with a plurality of contact members and ashort-circuiting device. Thus, receptacle 64, for example, is providedwith contact members 64a, 64b and 640, and a short-circuiting device 64dconnecting contact members 6412 and Mc. The plugs may be also. providedwith corresponding contact members and operating means for theshort-circuiting devices of the receptacles. Thus the plug 68, forexample, is provided with contact members 60a, 60b and 680, andoperating means End for operating the short-circuiting device 64d of thereceptacle B4.

The contact means of the plugs and receptacles cooperate to provideconnections between the pass control relays 40 through 42 and difierentones of the segments of the tracks 33 and 34 of the limit switch 32.These plugs and receptacles are designated as schedule #1 plugs andreceptacles on the drawing. Additional plugs I0, II and I2 may beprovided for positioning in additional receptacles I4 through I8 inorder to complete the #2 schedule connections. These plugs andreceptacles are designated as schedule #2 plugs and receptacles on thedrawing.

As shown, any one of the schedule #1 plugs may be positioned in any oneof the schedule #1 receptacles to provide control circuits for thedirectional relays 25 and 26 through the contact members of theassociated control relay and the segments of track 33, as well as acontrol circuit for the speed control relay 28 through the contactsegments of track 34 and one or more of the control resistors 36cthrough 36g. For example, the plug 60 for schedule #1 may be positionedin receptacle 3 so that a contact member 68a, of the plug 68 engagescontact member 84a of the receptacle 64. Contact members 601) and 660 ofthe plug 60 likewise engage contact members 64b and 640 of thereceptacle 64. The shortcircuiting device 6411 which normally connectscontact members 842) and 640 of the receptacle 64 is actuated by meansof the actuator or insulated projection 60d of the plug 68 after thecontact members 60a, 50c and 66b, 64c engage. Accordingly, an energizincircuit for one or another of the directional relays 25 and 26 will beprovided through the limit switch track 33, and movable arm 35,depending on in which receptacle the plug of an operated pass controlrelay is positioned, since this determines Where the break in the track33 occurs, and which of the directional relays 25 and 26 will beenergized. The speed of the screwdown motor I 5 also depends upon inwhich receptacle the plug of an operated relay is positioned, since thisdetermines how much of the control resistance 36 is included in thecircuit of the speed control relay 28.

Operation of the movable contact arm 35 to control the energizingcircuits for the directional relays 25 and 26 and the speed controlrelay 28 may be effected in any suitable manner such as by operativelyconnectin the operating shaft 31 to the screwdown motor I5 by means of asynchrotie system 80. This system may comprise a transmitter BI having arotor 82 connected to the shaft of the screwdown motor I5 and a stator83, and a receiver 84 having a rotor 85 electrically connected to therotor of the transmitter 8I through conductors 86 and a stator 81. Thestators 83 and 81 are connected for energy at or from a suitable sourceof alternating current represented by conductors 88.

In order to provide for making fine adjustmerits of the roll position, adifferential drive 89 may be interposed between the operating shaft 31and the receiver 84 to effect Vernier variations between the relativepositions of the contact arm 35 and the screwdown motor I5. Thedifferential drive 89 may comprise a pair of bevel gears 90 and 9|having a rotatable cage mounted therebetween with intermeshing bevelgears 92 mounted thereon. The cage may be connected to the rotor 85 ofthe receiver 84 through shaft 93 so as to be operated in accordance withthe operation of the screwdown motor I5 and position of the roll I2. Thebevel gear 98 may be connected to the operating shaft 3'! of the contactarm 35, while the bevel gear 9I may be provided with control means suchas the control motor 94 which is controlled by push button switches 95and 96 to raise or lower the roll I2 relative to the position normallycorresponding to the position of the contact arm 35.

With the limit switch in the position shown, if the movable contact arm48 of the pass selector switch 41 is actuated to the special passposition engaging contact member 41d, an obvious energizin circuit isestablished for the operating winding 5| of the special pass relay 58.Upon operation of relay 58 the contact arm 35 is connected to thenegative terminal of the source through contact members 5011, conductor91 and collector 38. This provides an energizing circuit for the lowerdirectional relay 26 extending from the negative terminal throughcontact members 50a, conductor 91, collector 38, operating shaft 31,contact arm 35, contact segment 33p of track 33, conductor 98, conductor99 which is shown as dotted since there may be a plurality ofreceptacles connected between those actually shown, short-circuitingdevice 6Bd, short-circuiting device Hid, conductor I08 which also isshown dotted since a plurality of other receptacles may be positionedbetween the receptacles actually shown, short-circuiting device 6511,short-circuiting device 15d, short-circuiting device 6401,short-circuitin device 14d, contact segment 33a, conductor I OI,operating winding I02 of the lower relay 26, and contact members 250 ofthe raise relay 25 to the positive terminal.

The operation of the lower directional relay 26 connects the fieldwinding 22 of the generator 2! to the source with such polarity as tocause the screwdown motor I5 to operate in the direction to lower themovable roll I2. The speed of operation of motor I5 which is determinedby the speed control relay 28 and. the pilot generator 3| will be atalmost a minimum since the energizing circuit for the operatin windin 29of the speed control relay 28 will be completed from the contact arm 35through segment 34q, resistor 36g, conductor I03, contact members 50b,conductor I04 through the pilot generator 3I, operating winding 29 andconductor 91 back to the arm 35.

Accordingly, the energization of the operating windin 29 will be almosta maximum, and the contact members 28a, 281), etc., of the speed controlrelay 28 will be separated, inserting most of the sections of the speedcontrol resistor 38 in the providing almost minimum field on thegenerator 2|. The motor l5 operates to move the roll I2 in the downwarddirection.

As soon as the rolls approach the minimum position, the speed of themotor I5 is reduced since the amount of the resistance 36 in theenergizing circuit for the operating winding 29 of the speed controlrelay 28 is reduced when the arm 35 engages the segment 3411. while itis still engaging the segment 33m. The operating winding 29 is thereuponenergized at a maximum and functions to overcome the biasing force sprin30, and the contact members of the speed control relay are separated amaximum, inserting all of the steps of the control resistor 30 in thecircuit of the field winding 22 so as to reduce the voltage applied tothe armature of the motor 15 to a minimum.

When the contact arm 35 leaves the contact segment 33!], the screwdownmotor stops, since the contact member 56c of the special pass controlrelay 5!] is open and the contact segment 33q is disconnected from theconductor HH and the operating winding I02 of the lower relay 26thereby. Accordingly, the circuit through the contact arm 35 isinterrupted and the lower directional relay 26 is deenergized, removingthe field from the generator 2| and causing the screwdown motor 15 tostop. A brake (not shown) may be applied in any well known manner forinsuring rapid stopping of the screwdown motor.

In order to set up a desired operating sequence, different ones of thepass plugs may be positioned in dilTerent ones of the receptacles,depending upon what roll spacing is desired for the particular pass. Forexample, the plug 66 may be positioned in the receptacle 64, while theplug 6| may be positioned in the receptacle 66 to provide for twodifierent passes during the operation of schedule #1. 7

It will be apparent, however, that any particular schedule may compriseany particular number of passes, and that the passes may be for any of anumber of difierent roll spacings. Likewise, any of the plugs 10 through12 may be positioned in different ones of the receptacles 74 through 18to set up schedule #2. For purposes of illustration it may be assumedplug number 16 may be positioned in receptacle while plug H ispositioned in receptacle l1. These connections are shown by dotted linesconnecting the respective plugs and receptacles.

The schedule selector switch 58 may now be operated to the #1 scheduleposition so as to connect the terminals of the operating windings 43through 45 of the pass control relays 40 through 42 to the positiveterminal of the source. When the contact arm of the pass selector switch41 1s positioned in engagement with the #1 pass contact 41a, a circuitfor the operating winding 43 of the #1 pass control relay 40 isprovided,extending from the negative terminal through contact arm 48, conductorH15, operating winding 43, contact segment I06 of the schedule selectorswitch 58 to the positive terminal of the source.

The control relay 40 operates, closing its contact members 4012 toconnect the contact arm 35 of the limit switch to the negative terminalthrough conductor 91, collector 38 and operating shaft 31. Since theshort-circuiting device 64d is operated to the open position by theactuator 60d of the plug 60, the energizing circuit for the lowerdirectional'rela'y 26 is interrupted. An

energizing circuit for the raise directional relay 25 is provided fromthe positive terminal through contact members 260, operating windingI68, conductor I69, contact members 21a of the interlocking relay 21,conductors H6 and H2, segments 331*, contact arm 35, shaft 31, conductor9i and contact members 40a to the negative terminal.

The raise relay 25 operates, connecting the field Winding 22 of thegenerator to the source through contact members 25a and 25b so that thescrewdown motor l5 operates to raise the roll l2. The speed of operationof the screwdown motor I5 is determined by the amount of the controlresistance 36 which is contained in the circuit of the operating winding29 of the speed control relay 28 and the armature of the pilot generator3!, as well as the speed of the pilot generator.

Since all of the resistance between the contact segment 34r and 34a isconnected in closed circuit relation with the pilot generator 3| and theoperating winding 29 through the circuit extending from contact members4% of the pass control relay 40, through contact member a of plug 60,contact member 64a of the receptacle 64, resistance 36, segment 341',contact arm 35, conductor 9i,- Winding 29, pilot generator 3| andconductor I04 to contact member 401;, the speed of the screwdown motorwill be almost a. maximum. As the contact arm 35 progresses towards theleft-hand end of the limit switch, the amount of the control resistance36 contained in the speed control circuit is reduced, thus reducing thespeed of the screwdown motor. Since the output of the pilot generator 3|is proportional to the speed of the screwdown motor, this factor tendsto balance or steady the speed at a predetermined desirable value.

Since contact members 400 of the control relay 40 are open, theenergizing circuit for the raise relay 25 will be interrupted as soon asthe contact arm 35 passes to the left of the contact segment 33b, whichis the last of the segments in the track 33 connected to the conductorH2 and hence to the operating winding I68 of the raise relay 25 throughthe short-circuiting contact devices of the receptacles. The motor l5stops and the roll I2 is in the desired position corresponding to thereceptacle 64 in which the pass plug 60 was positioned.

After a pass is completed with the roll l2 in the setting determined bythe pass plug 60 and pass control relay 46, the roll position may bechanged for pass #2 in schedule #1 by operating the contact arm 48 ofthe pass selector switch to the #2 pass position on contact 471). Assoon as the contact arm 48 leaves contact member 41a, the pass controlrelay 46 is deenergized. When the arm 48 engages contact member 41b, anenergizing circuit for the operating winding 44 of the #2 pass controlrelay M is provided. Relay 4| operates to connect the contact arm 35 tothe negative terminal through contact members 4Ia. With the pass plug 6|positioned in the receptacle 66, the actuator 6|d operates theshort-circuiting device 66a to interrupt the circuit between the contactsegments 33f and 33g.

Since the contact arm 35 had been previously moved to a positionengaging contact segment 33a of the limit switch, no energizing circuitis provided for the raise relay 25, and instead a control circuit isprovided for the lower relay 26. This circuit extends from the positiveterminal through contact members 250 of the raise relay, operatingwinding I02, conductor IOI, seg-- ment 33a, contact arm 35, operatingshaft 31, conductor 91, and contact members 4Ia to the negative terminalof the source. At the same time the operating circuit for the speedcontrol relay 28 is completed from the contact arm 35 through operatingshaft 31, conductor 91, operating winding 29, pilot generator 3|,conductor I04, contact members Mb, contact member 6Ia, contact member58a, conductor II8, control resistors 36d through 36a and segment 34a tothe contact arm 35.

Accordingly, the screwdown motor I operates at a moderate speed sincethe amount of resistance included in the speed control circuit is fairlylow. The speed is reduced gradually until the contact arm 35 engages thecontact segment 34c when the speed is reduced to a minimum, since all ofthe resistance 36 is then cut out and the maximum amount of the speedcontrol resistor 30 will then be inserted in the generator fieldcircuit. As'soon as the contact arm 35 leaves the contact segment33e,the energizing circuit for the lower relay 26 is interrupted, sincethe contact members 4Icbridging the short-circuiting device 66a areopen.

Should the screwdown motor I5 tend to overtravel, it cannot reversesince the interlocking relay 2?, which is energized through contactmembers 26d of the lower relay 26, interrupts the energizing circuit forthe "raise control relay 25 by opening contact members 21b. Theinterlocking relay 2'I seals itself in through contact members 21a,preventing operation of the raise relay until the pass selector switch4! is operated to a different position, during which operation theholding circuit for the interlocking relay 21 is interrupted.

Upon the completion of the #2 pass operation hereinbefore described,operations may be begun on the #2 schedule of operations by operatingthe schedule selector switch 58 to the #2 schedule position, therebyconnecting the operating windings 55, 55v and 51 of the #2 schedule passcontrol relays 52, 53 and 54 to the positive terminal of the sourcethrough contact member I20 of the schedule selector switch. It will beapparent, of course, that more than the two pass operations hereinbeforedescribed may be made during operations on schedule #1 and the number ofcontrol relays, plugs and receptacles may be much greater than actuallyshown since the actual number has been reduced in order to simplify thecircuit and facilitate explanation. Actually there may be a hundred ormore receptaclesand as many as eleven pass plugs and control relays foreach schedule.

With the schedule selector switch in the #2 position, the pass selectorswitch 41 may be operated to the #1 pass schedule #2 position engagingcontact member 4Ia, whereupon an energizing circuit is provided for theoperating winding 55 of the #2 schedule control relay 52. This circuitextends from the negative terminal, through contact arm 48, contactmember 41a, conductor I05, operating winding 55, conductor H9, contactsegment I20 to the positive terminal of the source. Control relay 52operates, connecting the contact arm 35 to the negative terminal throughcontact members 52a, and providing an operating circuit for the speedcontrol relay 28 through a circuit extending from the contact arm 35engaging contact segments 33f and 34a, through control resistors 36d to36b, conducto'r I22, to contact member 150. of receptacle 15, contactmember 10a of plug I0, contact members 52b to conductor I04 through thepilot generator 31, operating winding 29 of the speed control relay 28,conductor 91 to the operating shaft 3"! and contact arm 35. At the sametime an energizing circuit is provided for the raise relay 25 extendingfrom the positive terminal through contact members 260 of the lowerrelay 26, operating winding I08, conductor I09, contact members 27a,conductor IIO, conductor II2, contact members 500, conductor H4 and theshort-circuiting devices of the receptacles 68, i8, 61, I1 through 68and I5, segment 33] and contact arm 35, to the negative terminal of thesource through contact members 52a of the pass control relay 52.

Accordingly, the screwdown motor I'll operates to raise the roll I2 andactuate the contact arm 35 from right to left until it leaves thecontact member 336. Since the short-circuiting device 75d isopen-circuited, and the contact members 520 shunting theshort-circuiting device are also open, the contact segment 33b isdisconnected from the circuit to the right of the segment 33b, and theraise relay 25 becomes de-energized as soon as the contact arm 35 of thelimit switch reaches this segment. During the period of travel from thecontact segment 33] to the contact segment 331), the amount of thecontrol resistance 35 included in the speed control circuit of the speedcontrol relay 28 is gradually reduced so that the screwdown motor I5 isgradually slowed down to the stopping point. Successive passes may bemade in a manner previously described by operating the pass selectorswitch 41 to successively engage contact members 41b, 0, etc., for asmany pass plugs as may be positioned in the receptacles of theparticular schedule.

In Figs. 2 and 3, enlarged front elevational and sectional views of oneof the receptacles, for example the receptacle 64, are shown for thepurpose of describing in detail the construction and arrangement of theshort-circuiting device contained therein. As shown, the receptacle maycomprise an insulating support I24 positioned within a tubular casingI25 which may be mounted on a suitable base member I26. The support mayhave a plurality of terminals 64a, 64b and 640 mounted therein by meansof the terminal studs I27. The contact members 6401. through 640 may beof any construction, comprising, for example, tubular members I28 havingcutaway portions I30 on one side for receiving the inturned end portionsof a spring contact member I32.

The short-circuiting device 64d may comprise a pair of contact stripsI33 each having one end securely fastened between the tubular members ofthe contact members 64b and 640, respectively, and the insulatingsupport. The other ends thereof may be provided with upwardly inclinedportions I34 to provide inclined contact surfaces I35 on the lower sidepositioned in spaced relation to each other. A movable contact memberI36 may be provided, having a rounded end portion I31 for engaging thecontact surfaces, and being provided with means such as the spring I38for resiliently biasing it against the contact surfaces.

In order to ensure positive contact between the short-circuiting memberI36 and the adjacent contact surfaces I35 of the contact strips I33, thespring I38 may be disposed to actuate the short-circuiting member I36 ina direction which is inclined toward the contact surfaces. Thus, byproviding a recess I40 in the insulating support member intermediate thecontact strips I33, and which is inclined, toward the outer ends of thecontact strips, and making the recess I40 of slightly largercross-sectional dimensions than the short circuiting member I36, it ispossible to provide for some lateral movement of the shortcircuitingcontact member I36 along the contact surface of the contact strips I34both during engagement and disengagement of the short-circuiting contactmember and the contact strips.

Figs. 4 and 5 illustrate enlarged front end and sectional views of oneof the plugs such as, for example the plug 60, which it will be seen maycomprise a plurality of contact members or prongs 66a, 60b and 600mounted on an insulating support member I42. The insulating supportmember I42 may be positioned within a casing or housing comprising asubstantially tubular body portion I44 having a headed projection I46 atone end to provide a handle for gripping the plug, and an opening I41for receiving a plug cable I48 for making connections to the contactmembers.

In order to provide for operation of the shortcircuiting device 64d,means such as the actuator 60d may be provided comprising, for example,a rod of insulating material mounted in the insulating support I42 andprojecting slightly beyond the contact members 60a through 600. Theouter end of the actuator 60d may be provided with a reduced section I50disposed to be positioned between adjacent end portions of the contactstrips I33 of the receptacle, and having a bevel or inclined contactsurface I5I for engaging the rounded end surface of the shortcircuitingcontact member I31 in order to separate the contact member I31 from thecontact portions I34.

In order to provide a wiping or sliding action between the movableshort-circuiting contact member I36 and the contact portions I34 of thestrips 133, the relationship of the actuator slid to the movable contactmember I36 may be substantially as shown in the enlarged fragmentaryview in Fig. 6. From this view it will be clear that the inclinedsurface I SI of the actuator 80d engages the rounded end portion of themovable short-circuiting contact member I36 on the outer portion thereofon the side more remote from the contact strips I33, thus supplying anactuating force which is inclined to the longitudinal axis of theshort-circuiting member from the side which is more remote from thecontact strips I33.

Thus when the actuator 60d first engages the rounded end portion I3I ofthe movable shortcircuiting contact member I36, the short-circuitingmember is moved from its free or normal position against the outer wallof the recess I40 as shown by the dot-dash line I53 and slides along thecontact surface of the contact strip I34 until it strikes the inner wallportion of the recess I40. By this time the contact members a, 63b and600 have already engaged the contact members 64a, 64b, 640 of thereceptacle. Further movement of the plug into the receptacle actuatesthe short-circuiting contact member away from the contact strips I33,thus opening the circuit therebetween. When the plug is removed thiswiping action is repeated in reverse, and the spring slides the movablecontact member along the sloping contact surfaces I35 to a positionagainst the outer wall of the recess I40 as shown in Fig. 3.

By providing a plug and receptacle arrangement such as hereinbeforedescribed, it is possible to connect a plurality of the receptaclesbetween each of the contact segments of the limit switch and thusprovide for a plurality of rolling schedules. Since each of the plugs isconnected to a control relay having normally closed contact membersbridging the short-circuiting device, it will be apparent that differentschedules may be changed or set upon different groups of receptaclesduring the time that one schedule of rolling operations is beingperformed without interfering with the connections preset in said oneschedule.

In addition, by positioning the contact segments of one track instaggered relation to the contact segments ofthe other track, it ispossible to connect to the control resistors 36 intermediate the ends ofthe segments 34a through 34n and still provide for cutting out the laststep of resistance in order to effect operation of the screwdown motorat'the minimum speed, as it approaches the predetermined stoppingposition from either direction, at the same time reducing the number ofconnections and contact members required in each of the plugs andreceptacles.

Because the reversing operation of the screw down motor is prevented inthe event that the limit switch should slightly overshoot the desiredposition in the downward direction, further simplification of thecircuit is made possible so that the additional dead contact buttonsoriginally required with such limit switches may be dispensed with,together with the additional contact members required in each of theplugs and receptacles for making connections thereto.

Th inclusion of the short-circuiting device in the receptacle itselfeliminates the necessity for positioning dummy plugs in all of thereceptacles between passes in order to complete the necessary controlcircuits between adjacent segments for operating the screw-down motor.The elimination of these plugs greatly reduces the time required inmaking any one setup or in changing from one operating schedule toanother.

From the above description and the accompanying drawing, it will beapparent that I have provided a simple and effective manner forsimplifying and improving the control system for a screwdown orpositioning motor. The number of contact segments and amount of wiring,as Well as the number of contact points in the different plugs andreceptacles and the number of plugs required have been greatly reduced.

Accordingly, the limit switch may be made more compact, and the serviceand maintenance on the control apparatus are greatly reduced. Byincorporating the short-circuiting devices in the receptacles in themanner described, a plurality of schedules may be either preset orsubsequent schedules may be set up while rolling operations areproceeding on a previous setup schedule without any interferencetherebetween, and the need for dummy plugs to provide control circuitsbetween pass plugs is eliminated.

Since certain changes may be made in the above described construction,and different embodiments may be made without departing from the spiritand scope thereof, it is intended that all the matter contained in theabove description and shown in the accompanying drawings shall beconsidered as illustrative and not in a limited sense.

I claim as my invention:

1. In a control system for a plurality of relatively movable -rolls, areversible motor operable to adjust the position of one roll relative tothe other, control means selectively operable to effect operation of themotor in opposite directions, a limit'switch operable to determin thesense of operation of the control means and comprising a contact devicehaving an external circuit connection thereto and movable along apredetermined path in response to operation of the motor for engagingonly a pair of spaced apart tracks of contact segments positioned inend-to-end and spaced relation along said path, and a plurality ofcontrol devices selectively arranged for connection to predeterminedones of said segments tor providing an operating circuit for selectivelyoperating the control means to operate the screwdown motor to actuateone of the rolls to a predetermined position.

2. A control system for apair of relatively movable members comprising,a motor operativel'y connected to one of the members for moving itrelative to the other, control means selectively operable to effectoperation of the motor in opposite directions, a limit switch having acontact device movable along a predetermined path in response tomovement of said one member for engaging a pair of spaced apart tracksof spaced contact segments arranged in staggered relation, a pluralityof control devices disposed for connection to different ones of thesegments for providing a control circuit through a portion of one ofsaid tracks for selectively providing for operation of the controlmeans, and means including a plurality of resistors connected in seriesrelation with and having a connection from between each resistor to anadjacent segment of the other of said tracks for providing a controlcircuit for controlling the speed of the motor dependent on the distanceof the one member from the desired position.

3. A control system for a movable member comprising, a motor operable tomove the member to any of a plurality of positions, control meansdetermining the direction of operation or the motor, a limit switchhaving a contact member operatively connected to the motor for engaginga plurality of spaced segments forming spaced apart and substantiallyparallel tracks for controlling the operation of the control means, aplurality of control relays, a master control switch for selectivelyoperating said relays, and circuit means connecting the control relaysto predetermined ones of said segments for providing predeterminedcontrol circuits for the control means including a plurality ofreceptacles having short-clrcuiting devices for normally connecting thesegments of one track to each other and a plug associated with eachcontrol relay cooperative therewith to provide shunt circuits for theshort-circuiting devices.

4. A control system for a pair of relatively movable rolls having areversible motor for moving one of the rolls relative to the othercomprising, a limit switch having a pair of spaced tracks of segmentsdisposed in spaced and end-to-end relation with the segments of onetrack staggered relative to the segments in the other and having acontact member movable in response to movement of the movable roll, apair of control relays operable to effect operation of the motor inopposite directions, circuit means including a plurality of receptaclesfor providing circuits for operating the motor to position the movableroll in different predetermined positions, each of said receptacleshaving contact members connected to adjacent ends of segments of onetrack and to the segment of the other track opposite the ad-' jacentends, a plurality resistor means connected between adjacent segments ofthe other track, a master switch operable to a plurality of positions,control means operable to vary the speed of the motor, a plurality ofcontrol relays selectively op erable in accordance with differentpositions of the master switch, and a plug device associated with eachcontrol relay disposed to be positioned in one of the receptacles forcontrolling the connections between the segments of the one track andproviding a variable resistance circuit for the control means through aportion of said resistors depending on th distance of the movable rollfrom the desired position as determined by the plug device.

5. In a control system for a reversible positioning motor, control meansoperable to determine the direction or" operation of the motor,additional control means operable to determine the speed of the motor, alimit switch having a pair of spaced tracks of contact segments arrangedin staggered relation and a movable contact member positionable inaccordance with the position of the motor for engaging one track ofspaced segments to provide a preselected operating circuit for thecontrol means and for engaging the other track to provide a variableimpedance cir cuit for the additional control means, and a plurality ofcontrol relays selectively operable to determine said circuits.

6. A limit switch for an automatic screwdown control system comprising,a movable contact member, a pair of tracks of spaced contact segmentspositioned in side-by-side relation so as to be bridged by the movablecontact member, each of the segments in each track overlapping theadjacent segment to provide a substantially continuous conducting pathfor the contact member and the segments of the one track being sopositioned as to have the adjacent ends thereof substantiallyintermediate the ends of the segments of the other track, resistancemeans bridged between the segments of the one track, and switch meansconnecting adjacent segments of the other track operable to interruptthe connection therebetween.

'7. A limit switch for controlling the operation of a motor providedwith reversing means and speed control means comprising, a pair oftracks of elongated contact segments positioned in spaced andside-by-side relation with the segments of one track staggered relativeto the segments of the other, a movable contact member disposed inbridging relation between said tracks, and a plurality of resistancemeans connected in series circuit relation with connections intermediatethe resistors to adjacent segments of one track to provide a variableimpedance circuit for the speed control means.

8. A limit switch for a roll screwdown motor having associated therewitha pair of directional relays for controlling the direction of operationof the motor and speed control means for controlling the speed of themotor comprising, a pair of tracks of spaced contact segments positionedin side-by-side relation, a movable contact member disposed to beoperated in accordance with operation of the motor for bridging saidtracks, and a plurality of receptacles for effecting connections to saidsegments, each receptacle having short-circuiting means for normallyconnecting the adjacent ends of adjacent segments in one track toprovide an operating circuit in cooperation with the contact member forselectively' operating one or another of the directional relays and acontact means connected to the segment of the othertrack for providing acontrol circuit for the speed control means.

9. A limit switch for controlling the operation of a motor havingassociated therewith a pair of direction controlling relays, comprising,a plurality of elongated segments positioned in overlapping relation, amovable contact arm engaging said segments and movable in accordancewith the position of the motor, and circuit means providing an operatingcircuit for one or another of the directional relays including aplurality of receptacles having contact members connected to adjacentsegments and having movable contact means normally connecting saidcontact members to provide an operating circuit for one of the directioncontrolling relays.

10. The combination in a limit switch, of a pair of elongated trackscomprising spaced apart contact segments positioned in staggeredrelation with the adjacent ends of segments in one track 7 intermediatethe ends of a segment in the other track, a movable contact memberengaging said segments, a plurality of resistance elements connected inseries circuit relation and having a connection from between eachelement to an adjoining segment of one track, and a plurality ofreceptacles for efiecting connections to the segments including onecontact member connected intermediate each pair of the resistanceelements and a pair of contact members normally connected by a switchelement in the receptacle, said contact members being connected to theadjacent ends of the segments in the other track opposite the segmentsto which said one contact member is connected.

11. A limit switch comprising, a pair of tracks of elongated spacedapart segments disposed in side-by-side relation and positioned instaggered relation, resistance means bridging the segments of one track,a movable contact arm engaging said segments, and a plurality ofreceptacles having contact members for making external connections tothe segments, said receptacles being disposed in plural relation forproviding a plurality of different control circuits through the contactarm and segments with one contact member of each receptacle of eachgroup being connected between the resistance means bridging one segmentof said one track and the adjoining segments, and a pair of contactmembers of each receptacle of each group provided with shortcircuitingmeans and connected in series circuit relation between the adjacentsegments of the other track which are positioned opposite said onesegment.

12. A limit switch comprising, a pair of spaced apart tracks of spacedapart contact segments positioned in longitudinally. staggered relation,a movable contact arm positioned in bridging relation between saidtracks, driving means-operable to actuate the contact arm along saidtracks, a differential drive having a driven element connected toactuate the contact arm, a driving element operatively connected to saiddriving means, and an idling element operatively connecting the drivingand driven elements, said idling element being adjustable to vary theposition of the contact arm relative to the driving means.

13. A control system for a reversible motor operable to vary theposition of a movable member comprising, directional control meansoperable to control the direction of operation of the ceptacles havingstationary contacts and switch means cooperative therewith normallyconnecting adjacent ends of the segments of one track and additionalstationary contacts connected to the segment of the other track oppositethe adjacent ends of the segments in said one track, resistance meansconnected between adjacent segments of the other track, control meansincluding a master switch and a plurality of control relays selectivelyoperable under the control of the master switch, a plurality of plugmembers connected to said control relays and disposed to be positionedin said receptacles to provide difierent control circuits for thedirectional control means and the speed control means through thecontact arm and the segments of said one and said other track foroperating the motor to position the movable member to differentpositions depending on the operating position of the master switch andin which receptacles the plugs are positioned, and means for varying therelative position of the movable member relative to the position of thecontact arm comprising a differential device having a driven memberoperatively connected to the motor, a driving member operativelyconnected to the limit switch arm, and an idler member operativelyconnecting the driving and driven members, said idler member beingadjustable relative to the driving and driven members to vary theposition of the contact arm relative to the positions of the motor andthe movable member.

14. A control system for a screwdown motor operable to vary the positionof a pair of rolls relative to each other comprising, directionalcontrol means operable to determine the direction of operation of themotor, speed control means operable to vary the speed of the motor,means including a limit switch with a movable contact arm operativelyconnected to the screwdown motor and a plurality of tracks of spacedsegments for providing operating circuits for the directional controlmeans and the speed control means for operating the contact arm andmovable rolls in predetermined relation to predetermined positions, andVernier means comprising a difierential device interposed between themotor and the limit switch, said difierential device having anadjustable control element remotely operable to change the operatingconnec tion between the motor and the limit switch so as to permitchanging the position of the movable roll relative to the position ofthe limit switch.

WILLARD G. COOK.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,121,567 McWilliams Dec. 15,1914 1,414,709 Reisback Ma 2, 1922 1,711,397 Rumble Apr. 30, 19291,919,207 Douglas July 25, 1933 2,092,051 Cook Sept. 7, 1937 2,106,965Wright Feb. 1, 1938 2,144,033 Root Jan. 17, 1939 2,432,861 Cook Dec. 16,1947

